On Fri, 15 Oct 2021 21:58:38 GMT, Daniel D. Daugherty <dcu...@openjdk.org>
wrote:
>> src/hotspot/share/runtime/handshake.cpp line 358:
>>
>>> 356: bool target_is_dead = false;
>>> 357: if (target == nullptr) {
>>> 358: target_is_dead = true;
>>
>> Why would you pass a NULL target thread to Handshake::execute? Why would the
>> caller not check if the target is dead?
>
> The `NULL` target thread being passed in is actually handled by the baseline
> code:
>
>
> ThreadsListHandle tlh;
> if (tlh.includes(target)) {
>
>
> `tlh.includes(target)` returns `false` when `target` is `NULL/nullptr`.
> I just made the already handled situation more explicit.
>
>> Why would the caller not check if the target is dead?
>
> Hmmm... It's hard for me to answer that question since I didn't write
> the original code. The test code that calls `WB_HandshakeWalkStack()`
> or `WB_AsyncHandshakeWalkStack()` can call those functions with
> a `thread_handle` that translates into a `thread_oop` that returns a
> `NULL` `JavaThread*`.
>
> See the comment that I added to `WB_AsyncHandshakeWalkStack()` above.
Update: I've added comments to WB_HandshakeReadMonitors() and
WB_HandshakeWalkStack() to clarify their expectations.
-------------
PR: https://git.openjdk.java.net/jdk/pull/4677
